Thermionic amplifying device



Jan. 3, 1.933. s. W. BROWN THERMIONIC AMPLIFYING DEVICE Filed May 2,1929 2 Sheets-Sheet INVENTOR -STA/w. By W. .Bl'iaW/V 2 Sheets-SheetFiled May 2, 1929 STAN Patented Jan. 3, 1933 STANLEY W. BROWN, 0FBUFFALO, NEW YORK THERMIONIC AMPLIFYING DEVICE Application filed May 2,

My invention relates in general to devices for amplifying energies, andin particular to a device for use in connection with radio translatingdevices.

It is well known to those skilled in the art that in the ordinarythree-electrode thermionic device, such as the ordinary vacuum tube asused in a radio receiver, when the control or signal grid is negativelycharged, there is a very marked repelling action to the electronicstream due to this negative charge impressed on the grid by the negativehalf of the applied E. M. F. When the grid of such a tube is negativelycharged, many of the electrons are forced back to the cloud of electronsalready surrounding the cathode of the tube,'some of the electrons beingactuall forced back into the cathode surface, whic congestion isordinarily referred to as filament congestion. In such a vacuum tubethere is also capacity existing between the electrodes due toelectrostatic lines of force.

In an attempt to overcome some of the disadvantages above enumerated inconnection with the three-electrode'vacuum tube, radio engineers havedesigned a four-electrode vacuum tube, sometimes referred to as aplate-screen, or screen grid type tube. This tube substantiallyeliminates the capacity existing between the anode and the control grid,but the plate impedence of this tube is exceedingly high, and it is onlyat considerable cost and complication of construction that the maximumamplification of which this tube is capable is possible. It is,furthermore, well known that attempts have been made to change thefunction of the electrodes of this four-electrode vacuum tube and usethe plate-screens as a signal grid, while applying a positive potentialto that electrode which was originally designed to be used as a signalgrid. In such a make-shift use of this tube, exceedingly high capacityexists between the signal grid and the anode, and the amplification ofwhich the tube is capable is thus materially reduced.

In creating my invention, I have sought to provide a thermionic devicewhich shall have all the advantages of the vacuum tubes above 1929.Serial No. 359,813.

mentioned, but shall overcome the disadvantages thereof.

It has, therefore, been an object to produce a device in which thefilament congestion and space charge shall be relieved, and in Which thedensity and uniformity of the electronic stream shall be increased.

Other objects are to increase the mutual conductance; to increase theamplification constant; and to reduce the plate impedance.

Moreover, in my device, the inter-electrode capacity is greatly reduced.

Furt ermore, because my invention reduces the plate impedence, it ispossible through simpler and more economical structures to get maximumamplification.

In my device, in addition to the customary cathode, anode, signal grid,and plate screens, I also use an additional electrode which ispreferably in the form of a grid located between the filament andcontrol grid in direct current types, and between the cathode andcontrol grid in the alternating current types. To this fifth electrodeis applied a definite and constant otential or influence. Because of thepotential applied and geometric location of this fifth electrode in thetube with respect to the electron emitting electrode, it has a greatower of attraction for the electrons. In act, the action of thiselectrode could almost be described as having a sucking effect upon theelectrons from the filament or cathode, and, therefore, the negativecloud of electrons surrounding the filament or cathode is broken up. Theaction relieves filament congestion and hence clears the path for a freeand dense electronic stream between the electron emitter and the anode.Since as is well known, the sensitivity of the control of the signalgrid is definitely limited by the negative cloud of electronssurrounding the electron emitter, my device has a wider control range ofthe signal grid, and, therefore, greater amplifying ability because ofthe fact that the electronic congestion is relieved.

The above objects and advantages have been accomplished by the deviceshown in the accompanying drawings, of which:

Fig. 1 is an exterior view of my complete device.

Fig. 2 is an enlarged fragmentary, vertical, sectional elevationthereof, showing the various parts of the device in somewhat of a diaammatic manner.

ig. 3 is a sectional plan view of my device, and is taken on line 3-3 ofFig. 2.

Figs. 4, 5, and 6 are diagrammatic views showlng typical circuitarrangements for emplo ing my device in a system for the ampli cation ofelectromagnetic impulses.

Referring to Figs. 1 to 3, inclusive, it will be seen that my device ismade up in the form of the standard vacuum tube, and comprises a base 10carrying the usual evacuated envelope 11, within which the electrodes ofmy device are disposed. As is customary the envelope is formed with theglass stem 12 which carries the supporting and anchoring wires for thevarious electrodes.

The stem 12 carries two upwardly extending supporting wires 13 to theupper portions of which is secured the anode 14 of my device. This anodeis preferably in the form of a cylindrically shaped plate and is securedby any suitable means to the supports 13. This anode 14 is surrounded byan outer anode screen 15 which is arranged in interspaced relationtherewith. This screen is preferably made in the form ofa helix, theturns of which are supported at diametrically opposite sides by'ineansof wire support 16. The lower ends of these wire supports are fastenedtogether by means of a horizontally arranged circular brace 17. Arrangedover the upper end of the outer anode screen 15 is a shielding plate 18for the anode which is preferably of substantially the same size as thediameter of the outer anode shield, and which is securely fastened tothe upper ends of the wire supports 16. This plate is provided initscenter with an aperture 19 for the passage of other of the electrodes ofthe device, to be hereinafter described. The extreme upper ends of thewire supports 16 are attached to horizontal supporting wires 20 whichare carried by the glass brace or bridge 21 to be hereinafter described.Arranged within and in interspaced relation with the anode 14 is aninner anode screen 25. This anode screen is also made of wire and may behelical in form. This inner screen is provided at diametrically oppositesides with supporting wires 26. The lower ends of these supporting wiresare carried by the stem 12 and they extend upwardly and have their upperends securely fastened to the shielding plate 18. The inner and outeranode screens 25 and 15, respectively, are. therefore, mechanically andelectrically tied together at their upper ends. The lower ends areconnected together by means of a lead 27 which connects the horizontalcircular brace 17 with one of the supporting wires 26.

Arranged within the inner anode screen 25 is the signal grid 30. Thisgrid is preferably cylindrical in form and has a supporting wire 31arranged at one side thereof. The upper end of this supporting wireextends through the opening 19 in the shielding plate 18 and issupported by means of the horizontal supporting wire 32 carried by theglass bridge 21. The lower end of the supporting wire 31 is carried byan insulating head 33 preferably of glass. Arranged concentricallywithin the grid 30 is the cathode screen 34 of my device. This electrodemay be in the form of a helix, which is carried by a supporting wire 35extending through the electrode and at one side thereof. The lower endof this Wire is supported by the glass stem 12 of the device while theupper end thereof is attached to the horizontal supporting wire 36 ofthe glass bridge 21. A supporting wire 29 is attached near the lower endof the supporting wire 35, and its upper end is mounted in the insulator33, whereby the insulator and the signal grid is supported. Arrangedconcentrically through the cathode screen 34 is the cathode or filament37 of my device. This electrode is preferably in the form of a singlewire, in direct current types, and is supported at its lower end by aconductor 38, carried by the stem 12, and at its upper end by aconductor 39. The conductor 39 extends horizontally from the upper endof the filament 37 and is provided with a vertical portion 40 whichpasses through the bridge 21 and extends downwardly to a pointsubstantially opposite the stem 12. A horizontally arranged conductor 41has its outer end attached to the vertical conductor 40, and its innerend 42 bent downwardly and secured in the stem 12. Carried by the top ofthe envelope 11 is a signal grid cap 45 which is connected preferably tothe supporting wire 31 of the signal grid 30 by means of a lead 46. Thelower end of the conductor 40 is preferably provided with an inwardlybent portion 47 at the inner end of which is a metal foot 48 whichcarries the customary getter 49.

Carried by the base are the prongs of my device, comprising a negativefilament prong 50, a positive filament prong 51, a cathode screen prong52, an anode prong 53, and an inner and outer anode shield prong 54. Thenegative filament prong 50 is connected to the conductor 38 by means ofa lead 55, while the positive filament prong 51 is connected to the end42 of the horizontal conductor 41 by means of a lead 56. The cathodescreen prong 52 is connected by means of a lead 57 to the conductor 35.The anode prong 53 is connected to one of the supporting wires 13 of theanode by means of a lead 58. The inner and outer anode screen prong 54is connected with one of the supporting wires 26 by means of a lead 59.

Referring now to the diagrams, Fig. 4

lol

. potential received by 65' nected between represents atransformer-coupled, radio receiving circuit; Fig. 5 shows atunedimpedence circuit; and Fig. 6 shows an autotransformer circuit. Ineach of these circuits represents the antenna; 61 represents the primarywinding of theantenna inductance 62; and 63 represents the secondarywinding of the antenna inductance. A variable condenser 64 is shuntedacross the secondary winding 63 of the antenna inductance for thepurpose of tuning this circuit.

Referring now more specifically to the transformer-coupled circuit ofFig. 4, it will be seen that the signal or control grid 30 is connectedby means of a lead 65 to one side of the secondary winding 63 of theantenna inductance, while the other side of this winding is connected,in cases where a grid bias battery 93 is used, by means of a lead 98 tothe negative side of the battery. The positive side of the battery 93will be connected by means of a lead 66 to the negative side of the hi hpotential battery 67. The positive side 0% the high potential battery 67is connected by means of a lead 68 to one side of the rimary 69 of theradio frequency transormer 70. The other side of this winding isconnected to the anode or plate 14 of my device by means of: a lead 71.Of course, when the grid bias battery 93 is not used, the leads 98 and66 are connected together, or the battery is replaced by a resistance.variable condenser 72 may be used, and when used, is shunted across theprimary winding 69, whereby this winding is tuned. The filament 37' indirect current types is connected to a battery 7 3 of low potentialthrough a rheostat 74 for controlling the heat of the filament. In thisand the other types of circuits shown in Figs. 5 and 6, it is obviousthat the battery 73 and the rheostat 74 will be omitted when the deviceis to be usedon alternating currents. It will be clear that 75 is thesecondary winding of the radio frequency transformer 70, and this isconnected to the output terminals 76 and 77. A variable condenser 78 isprovided for tuning the secondary winding 75. Ihe inner and outer anodescreens 25 and 15, respectively, are connectedby means of a lead 79 tothe high potential battery the screens may be varied. A lead 80 connectsthe lead 66 extending to the negative side of the high potential battery67 with one side of the filament 37, and a fixed condenser 81 isconnected across leads 79 and 80 for furnishing a path for highfrequency current from the anode screens 25 and 15 to the filament 37.The cathode screen 34 is connected to the lead 66 through a battery 82by means of a lead 88, whereby this screen is supplied with a positivepotential. A fixed condenser 84 is conthe' filament 37 and the lead Atially 67 in such a manner that the 9 83 for the passage of highfrequency currents.

In the impedence tuned circuit of Fig. 5, the connections to the variousparts of my device are substantially the same as those above describedin connection with Fig. 4 except that the positive side of the highpotential battery is connected to one side of an impedance 85. the otherend of this impedance being connected to a lead 86, the impedance beingprovided. with a condenser 92 for tuning the same. One end of the lead86 is connected to the anode 14, while the other end is connected to oneof the output terminals 87 through a coupling condenser 88. The otheroutput terminal 89 is connected to a lead 90, and a level 91 connectsthe lead with the negative side of the filament 37 When a grid biasbattery 93 is employed in the circuits of Figs. 5 and 6, the positiveside of the battery is connected to the lead 90, and the negative sideto the grid return end of the secondary winding 63 of the antennainductance 62 by means of a lead 99. A variable resistance 95 is placedbetween the output terminals 87 and 89. In alternating current types, asis well known, the return leads are brought back to the cathode terminalinstead of the filament.

In the autotransformer arrangement shown in Fig. 6 the connections aresubstanthe same as in the circuit arrangement of Fig. 5, except that anautotransformer 96 is connected between the lead 90 and the outputterminal 87, the coupling condenser 88 being connected to the variabletap of the autotransformer by means of a lead 100. The autotransformeris provided with a variable condenser 97 for tuning the same.

While I have shown and described my invention as ap lied to directcurrent types, this is simply or illustrative purposes, and it isobvious that my invention is applicable to alternating current types aswell. Obviously, when my invention is used as an alternating currentdevice, the grid bias battery 93 will be replaced by suitableresistance.

It is preferable in the above described circuits to provide a by-passaround the high potential battery 67 by means of a condenser If desired,a high impedance winding may be inserted in the screen grid circuit, andone may also be placed in the cathode screen circuit for the purpose offurther stabilization.

For convenience in the appended claims, I have referred to the circuitwhich includes the anode screen as the anode screen circuit; the circuitwhich includes the cathode screen as the cathode screen circuit; and thecircuit which includes the cathode as the cathode circuit.

While I have shown man trodes of my device as being of the elecormed ofwire in helical. shape, it is obvious that a'wire gauze or wire mesh maybe used if desired.

v I These and other modifications of the details herein shown anddescribed may be made without departing from the spirit of my inventionor the scope of the appended claims, and I do not, therefore, wash to belimited to the exact embodiment herein shown and described, the formshown being merely a preferred embodiment thereof.

Having thus described my invention, what I claim is:

A thermionic amplifying device, comprising an electron emitting cathode,an anode, a signal grid located between the cathode and the anode, aninner screen located between the anode and the signal grid, a cathodescreen between the signal grid and the cathode, and

an outer anode screen surrounding the anode. In testimony whereof, Ihave hereunto signed my name.

' STANLEY W. BROWN.

